Wells are generally drilled into the ground or ocean bed to recover natural deposits of oil and gas, as well as other desirable materials that are trapped in geological formations in the Earth's crust. Wells are typically drilled using a drill bit attached to the lower end of a “drill string.” Drilling fluid, or mud, is typically pumped down through the drill string to the drill bit. The drilling fluid lubricates and cools the bit, and may additionally carry drill cuttings from the borehole back to the surface.
In various oil and gas exploration operations, it may be beneficial to have information about the subsurface formations that are penetrated by a borehole. For example, certain formation evaluation schemes include measurement and analysis of the formation pressure and permeability. These measurements may be essential to predicting the production capacity and production lifetime of the subsurface formation.
Further, in addition to the formation testing tools, which may be primarily used to collect fluid samples, samples may also be taken of the formation rock within the borehole. For example, a coring tool may be used to take a core of the formation rock within the borehole. The typical coring tool usually includes a hollow drill bit, such as a coring bit, that is advanced into the formation wall such that a sample, such as a core, may be removed from the formation. Downhole coring operations generally include axial coring and sidewall coring. In axial coring, the coring tool may be disposed at the end of a drill string disposed within a borehole, in which the coring tool may be used to collect a core at the bottom of the borehole. In sidewall coring, the coring bit from the coring tool may extend radially from the coring tool, in which the coring tool may be used to collect a core from a side wall of the borehole.
As such, the core may then be transported to the Earth's surface, in which the sample may be analyzed to assess the porosity and the permeability of the material that makes up the formation surrounding the borehole, amongst other things such as the chemical and mineral composition of the fluids and mineral deposits contained in the pores of the formation and/or the irreducible water content contained in the formation. However, traditional coring tools may be limited in operation, such as by having limited storage area for cores, and further may not reliably break core samples away from the formation of the borehole.